/** @file
  TCG MOR (Memory Overwrite Request) Lock Control support (SMM version).

  This module initilizes MemoryOverwriteRequestControlLock variable.
  This module adds Variable Hook and check MemoryOverwriteRequestControlLock.

Copyright (c) 2016 - 2018, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution.  The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include <PiDxe.h>
#include <Guid/MemoryOverwriteControl.h>
#include <IndustryStandard/MemoryOverwriteRequestControlLock.h>
#include <Library/DebugLib.h>
#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include "Variable.h"

typedef struct {
  CHAR16                                 *VariableName;
  EFI_GUID                               *VendorGuid;
} VARIABLE_TYPE;

VARIABLE_TYPE  mMorVariableType[] = {
  {MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,      &gEfiMemoryOverwriteControlDataGuid},
  {MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,  &gEfiMemoryOverwriteRequestControlLockGuid},
};

BOOLEAN         mMorPassThru = FALSE;

#define MOR_LOCK_DATA_UNLOCKED           0x0
#define MOR_LOCK_DATA_LOCKED_WITHOUT_KEY 0x1
#define MOR_LOCK_DATA_LOCKED_WITH_KEY    0x2

#define MOR_LOCK_V1_SIZE      1
#define MOR_LOCK_V2_KEY_SIZE  8

typedef enum {
  MorLockStateUnlocked = 0,
  MorLockStateLocked = 1,
} MOR_LOCK_STATE;

BOOLEAN         mMorLockInitializationRequired = FALSE;
UINT8           mMorLockKey[MOR_LOCK_V2_KEY_SIZE];
BOOLEAN         mMorLockKeyEmpty = TRUE;
BOOLEAN         mMorLockPassThru = FALSE;
MOR_LOCK_STATE  mMorLockState = MorLockStateUnlocked;

/**
  Returns if this is MOR related variable.

  @param  VariableName the name of the vendor's variable, it's a Null-Terminated Unicode String
  @param  VendorGuid   Unify identifier for vendor.

  @retval  TRUE            The variable is MOR related.
  @retval  FALSE           The variable is NOT MOR related.
**/
BOOLEAN
IsAnyMorVariable (
  IN CHAR16                                 *VariableName,
  IN EFI_GUID                               *VendorGuid
  )
{
  UINTN   Index;

  for (Index = 0; Index < sizeof(mMorVariableType)/sizeof(mMorVariableType[0]); Index++) {
    if ((StrCmp (VariableName, mMorVariableType[Index].VariableName) == 0) &&
        (CompareGuid (VendorGuid, mMorVariableType[Index].VendorGuid))) {
      return TRUE;
    }
  }
  return FALSE;
}

/**
  Returns if this is MOR lock variable.

  @param  VariableName the name of the vendor's variable, it's a Null-Terminated Unicode String
  @param  VendorGuid   Unify identifier for vendor.

  @retval  TRUE            The variable is MOR lock variable.
  @retval  FALSE           The variable is NOT MOR lock variable.
**/
BOOLEAN
IsMorLockVariable (
  IN CHAR16                                 *VariableName,
  IN EFI_GUID                               *VendorGuid
  )
{
  if ((StrCmp (VariableName, MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME) == 0) &&
      (CompareGuid (VendorGuid, &gEfiMemoryOverwriteRequestControlLockGuid))) {
    return TRUE;
  }
  return FALSE;
}

/**
  Set MOR lock variable.

  @param  Data         MOR Lock variable data.

  @retval  EFI_SUCCESS            The firmware has successfully stored the variable and its data as
                                  defined by the Attributes.
  @retval  EFI_INVALID_PARAMETER  An invalid combination of attribute bits was supplied, or the
                                  DataSize exceeds the maximum allowed.
  @retval  EFI_INVALID_PARAMETER  VariableName is an empty Unicode string.
  @retval  EFI_OUT_OF_RESOURCES   Not enough storage is available to hold the variable and its data.
  @retval  EFI_DEVICE_ERROR       The variable could not be saved due to a hardware failure.
  @retval  EFI_WRITE_PROTECTED    The variable in question is read-only.
  @retval  EFI_WRITE_PROTECTED    The variable in question cannot be deleted.
  @retval  EFI_SECURITY_VIOLATION The variable could not be written due to EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS
                                  set but the AuthInfo does NOT pass the validation check carried
                                  out by the firmware.
  @retval  EFI_NOT_FOUND          The variable trying to be updated or deleted was not found.
**/
EFI_STATUS
SetMorLockVariable (
  IN UINT8  Data
  )
{
  EFI_STATUS  Status;

  mMorLockPassThru = TRUE;
  Status = VariableServiceSetVariable (
             MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,
             &gEfiMemoryOverwriteRequestControlLockGuid,
             EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
             sizeof(Data),
             &Data
             );
  mMorLockPassThru = FALSE;
  return Status;
}

/**
  This service is an MorLock checker handler for the SetVariable().

  @param  VariableName the name of the vendor's variable, as a
                       Null-Terminated Unicode String
  @param  VendorGuid   Unify identifier for vendor.
  @param  Attributes   Point to memory location to return the attributes of variable. If the point
                       is NULL, the parameter would be ignored.
  @param  DataSize     The size in bytes of Data-Buffer.
  @param  Data         Point to the content of the variable.

  @retval  EFI_SUCCESS            The MorLock check pass, and Variable driver can store the variable data.
  @retval  EFI_INVALID_PARAMETER  The MorLock data or data size or attributes is not allowed.
  @retval  EFI_ACCESS_DENIED      The MorLock is locked.
  @retval  EFI_WRITE_PROTECTED    The MorLock deletion is not allowed.
  @retval  EFI_ALREADY_STARTED    The MorLock variable is handled inside this function.
                                  Variable driver can just return EFI_SUCCESS.
**/
EFI_STATUS
SetVariableCheckHandlerMorLock (
  IN CHAR16     *VariableName,
  IN EFI_GUID   *VendorGuid,
  IN UINT32     Attributes,
  IN UINTN      DataSize,
  IN VOID       *Data
  )
{
  EFI_STATUS  Status;

  //
  // Basic Check
  //
  if (Attributes == 0 || DataSize == 0 || Data == NULL) {
    //
    // Permit deletion for passthru request, deny it otherwise.
    //
    return mMorLockPassThru ? EFI_SUCCESS : EFI_WRITE_PROTECTED;
  }

  if ((Attributes != (EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS)) ||
      ((DataSize != MOR_LOCK_V1_SIZE) && (DataSize != MOR_LOCK_V2_KEY_SIZE))) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // Do not check if the request is passthru.
  //
  if (mMorLockPassThru) {
    return EFI_SUCCESS;
  }

  if (mMorLockState == MorLockStateUnlocked) {
    //
    // In Unlocked State
    //
    if (DataSize == MOR_LOCK_V1_SIZE) {
      //
      // V1 - lock permanently
      //
      if (*(UINT8 *)Data == MOR_LOCK_DATA_UNLOCKED) {
        //
        // Unlock
        //
        Status = SetMorLockVariable (MOR_LOCK_DATA_UNLOCKED);
        if (!EFI_ERROR (Status)) {
          //
          // return EFI_ALREADY_STARTED to skip variable set.
          //
          return EFI_ALREADY_STARTED;
        } else {
          //
          // SetVar fail
          //
          return Status;
        }
      } else if (*(UINT8 *)Data == MOR_LOCK_DATA_LOCKED_WITHOUT_KEY) {
        //
        // Lock without key
        //
        Status = SetMorLockVariable (MOR_LOCK_DATA_LOCKED_WITHOUT_KEY);
        if (!EFI_ERROR (Status)) {
          //
          // Lock success
          //
          mMorLockState = MorLockStateLocked;
          //
          // return EFI_ALREADY_STARTED to skip variable set.
          //
          return EFI_ALREADY_STARTED;
        } else {
          //
          // SetVar fail
          //
          return Status;
        }
      } else {
        return EFI_INVALID_PARAMETER;
      }
    } else if (DataSize == MOR_LOCK_V2_KEY_SIZE) {
      //
      // V2 lock and provision the key
      //

      //
      // Need set here because the data value on flash is different
      //
      Status = SetMorLockVariable (MOR_LOCK_DATA_LOCKED_WITH_KEY);
      if (EFI_ERROR(Status)) {
        //
        // SetVar fail, do not provision the key
        //
        return Status;
      } else {
        //
        // Lock success, provision the key
        //
        mMorLockKeyEmpty = FALSE;
        CopyMem (mMorLockKey, Data, MOR_LOCK_V2_KEY_SIZE);
        mMorLockState = MorLockStateLocked;
        //
        // return EFI_ALREADY_STARTED to skip variable set.
        //
        return EFI_ALREADY_STARTED;
      }
    } else {
      ASSERT (FALSE);
      return EFI_OUT_OF_RESOURCES;
    }
  } else {
    //
    // In Locked State
    //
    if (mMorLockKeyEmpty || (DataSize != MOR_LOCK_V2_KEY_SIZE)) {
      return EFI_ACCESS_DENIED;
    }
    if ((CompareMem (Data, mMorLockKey, MOR_LOCK_V2_KEY_SIZE) == 0)) {
      //
      // Key match - unlock
      //

      //
      // Need set here because the data value on flash is different
      //
      Status = SetMorLockVariable (MOR_LOCK_DATA_UNLOCKED);
      if (EFI_ERROR (Status)) {
        //
        // SetVar fail
        //
        return Status;
      } else {
        //
        // Unlock Success
        //
        mMorLockState = MorLockStateUnlocked;
        mMorLockKeyEmpty = TRUE;
        ZeroMem (mMorLockKey, sizeof(mMorLockKey));
        //
        // return EFI_ALREADY_STARTED to skip variable set.
        //
        return EFI_ALREADY_STARTED;
      }
    } else {
      //
      // Key mismatch - Prevent Dictionary Attack
      //
      mMorLockState = MorLockStateLocked;
      mMorLockKeyEmpty = TRUE;
      ZeroMem (mMorLockKey, sizeof(mMorLockKey));
      return EFI_ACCESS_DENIED;
    }
  }
}

/**
  This service is an MOR/MorLock checker handler for the SetVariable().

  @param[in]  VariableName the name of the vendor's variable, as a
                           Null-Terminated Unicode String
  @param[in]  VendorGuid   Unify identifier for vendor.
  @param[in]  Attributes   Attributes bitmask to set for the variable.
  @param[in]  DataSize     The size in bytes of Data-Buffer.
  @param[in]  Data         Point to the content of the variable.

  @retval  EFI_SUCCESS            The MOR/MorLock check pass, and Variable
                                  driver can store the variable data.
  @retval  EFI_INVALID_PARAMETER  The MOR/MorLock data or data size or
                                  attributes is not allowed for MOR variable.
  @retval  EFI_ACCESS_DENIED      The MOR/MorLock is locked.
  @retval  EFI_ALREADY_STARTED    The MorLock variable is handled inside this
                                  function. Variable driver can just return
                                  EFI_SUCCESS.
**/
EFI_STATUS
SetVariableCheckHandlerMor (
  IN CHAR16     *VariableName,
  IN EFI_GUID   *VendorGuid,
  IN UINT32     Attributes,
  IN UINTN      DataSize,
  IN VOID       *Data
  )
{
  //
  // do not handle non-MOR variable
  //
  if (!IsAnyMorVariable (VariableName, VendorGuid)) {
    return EFI_SUCCESS;
  }

  //
  // MorLock variable
  //
  if (IsMorLockVariable (VariableName, VendorGuid)) {
    return SetVariableCheckHandlerMorLock (
             VariableName,
             VendorGuid,
             Attributes,
             DataSize,
             Data
             );
  }

  //
  // Mor Variable
  //

  //
  // Permit deletion for passthru request.
  //
  if (((Attributes == 0) || (DataSize == 0)) && mMorPassThru) {
    return EFI_SUCCESS;
  }

  //
  // Basic Check
  //
  if ((Attributes != (EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS)) ||
      (DataSize != sizeof(UINT8)) ||
      (Data == NULL)) {
    return EFI_INVALID_PARAMETER;
  }
  if (mMorLockState == MorLockStateLocked) {
    //
    // If lock, deny access
    //
    return EFI_ACCESS_DENIED;
  }
  //
  // grant access
  //
  return EFI_SUCCESS;
}

/**
  Initialization for MOR Control Lock.

  @retval EFI_SUCCESS     MorLock initialization success.
  @return Others          Some error occurs.
**/
EFI_STATUS
MorLockInit (
  VOID
  )
{
  mMorLockInitializationRequired = TRUE;
  return EFI_SUCCESS;
}

/**
  Delayed initialization for MOR Control Lock at EndOfDxe.

  This function performs any operations queued by MorLockInit().
**/
VOID
MorLockInitAtEndOfDxe (
  VOID
  )
{
  UINTN      MorSize;
  EFI_STATUS MorStatus;

  if (!mMorLockInitializationRequired) {
    //
    // The EFI_SMM_FAULT_TOLERANT_WRITE_PROTOCOL has never been installed, thus
    // the variable write service is unavailable. This should never happen.
    //
    ASSERT (FALSE);
    return;
  }

  //
  // Check if the MOR variable exists.
  //
  MorSize = 0;
  MorStatus = VariableServiceGetVariable (
                MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
                &gEfiMemoryOverwriteControlDataGuid,
                NULL,                                   // Attributes
                &MorSize,
                NULL                                    // Data
                );
  //
  // We provided a zero-sized buffer, so the above call can never succeed.
  //
  ASSERT (EFI_ERROR (MorStatus));

  if (MorStatus == EFI_BUFFER_TOO_SMALL) {
    //
    // The MOR variable exists.
    //
    // Some OSes don't follow the TCG's Platform Reset Attack Mitigation spec
    // in that the OS should never create the MOR variable, only read and write
    // it -- these OSes (unintentionally) create MOR if the platform firmware
    // does not produce it. Whether this is the case (from the last OS boot)
    // can be deduced from the absence of the TCG / TCG2 protocols, as edk2's
    // MOR implementation depends on (one of) those protocols.
    //
    if (VariableHaveTcgProtocols ()) {
      //
      // The MOR variable originates from the platform firmware; set the MOR
      // Control Lock variable to report the locking capability to the OS.
      //
      SetMorLockVariable (0);
      return;
    }

    //
    // The MOR variable's origin is inexplicable; delete it.
    //
    DEBUG ((
      DEBUG_WARN,
      "%a: deleting unexpected / unsupported variable %g:%s\n",
      __FUNCTION__,
      &gEfiMemoryOverwriteControlDataGuid,
      MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME
      ));

    mMorPassThru = TRUE;
    VariableServiceSetVariable (
      MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
      &gEfiMemoryOverwriteControlDataGuid,
      0,                                      // Attributes
      0,                                      // DataSize
      NULL                                    // Data
      );
    mMorPassThru = FALSE;
  }

  //
  // The MOR variable is absent; the platform firmware does not support it.
  // Lock the variable so that no other module may create it.
  //
  VariableLockRequestToLock (
    NULL,                                   // This
    MEMORY_OVERWRITE_REQUEST_VARIABLE_NAME,
    &gEfiMemoryOverwriteControlDataGuid
    );

  //
  // Delete the MOR Control Lock variable too (should it exists for some
  // reason) and prevent other modules from creating it.
  //
  mMorLockPassThru = TRUE;
  VariableServiceSetVariable (
    MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,
    &gEfiMemoryOverwriteRequestControlLockGuid,
    0,                                          // Attributes
    0,                                          // DataSize
    NULL                                        // Data
    );
  mMorLockPassThru = FALSE;

  VariableLockRequestToLock (
    NULL,                                       // This
    MEMORY_OVERWRITE_REQUEST_CONTROL_LOCK_NAME,
    &gEfiMemoryOverwriteRequestControlLockGuid
    );
}
